Taking the drug suvorexant increased the amount of time people spent asleep during the night, according to the study. The study involved 254 people ages 18 to 64 who were in good physical and mental health but had insomnia that was not due to another medical condition.

The participants took either the drug or a placebo for four weeks, then switched to the other treatment for another four weeks. The participants spent the night in a sleep laboratory with their sleep monitored on the first night with each treatment and then again in the fourth week of each treatment.

While taking the drug, participants' "sleep efficiency," which reflects the total amount of time they slept during a fixed, eight hour time in bed, improved by 5 to 13 percent compared to those taking the placebo. They also experienced 21 to 37 fewer minutes awake during the night after they had fallen asleep than those who took the placebo.

"This study provides evidence that suvorexant may offer a successful alternative strategy for treating insomnia," said study author W. Joseph Herring, MD, PhD, of North Wales, Penn., Executive Director of Clinical Research with Merck, the maker of suvorexant, and a member of the American Academy of Neurology. "Suvorexant was generally well-tolerated, and there were no serious side effects."

Herring said larger, longer studies have recently been conducted on suvorexant, along with studies to determine whether the drug could be safe and effective for elderly people, who make up a large percentage of those suffering from insomnia.